Method of plating aluminium



v (NoModeL) W. H. LEGATE.

METHOD OF PLATING ALUMINIUM. No. 536,152. Patented Mar. 19, 1895.

Ema.

UNITED STATES PATENT OFFICE.

WILLIAM H. LEGATE, OF HARTFORD, CONNECTICUT.

METHOD OF PLATING ALUMINIUM.

SPECIFICATION forming part of Letters Patent No. 536,152, dated March 19, 1895.

Application filed July 18,1894- Serial No. 517,896. (No specimens.)

To all whom it may concern:

Be it known that 1, WILLIAM H. LEGATE, of Hartford, in the county of Hartford and State of Connecticut, have invented certain new and useful Improvements in Aluminium-Plating, of which the following is a full, clear, and exact description.

'The object of my invention is to provide a method of and means for plating upon aluminum without regard to the special material used for such purpose.

To this end my invention consists in the process, and in the combination of the several steps of the process and materials to constitute the several baths and solutions, as more particularly hereinafter described and points 6. out in the claims.

Referring to the drawings: Figure 1 is a diagram view illustrating an arrangement of the several solutions and dips. Fig. 2 is a diagram view illustrating the arrangement of the whiteners.

A great many attempts have been made and experiments tried to secure a method of coverin g or protecting the surface of an article made of aluminum or analuminum alloy with a surface layer of metal. more durable or of higher value, but the difficulty in all prior methods has been to produce a plated surface which would hold firmly and not strip or peel off.

As commercially used in the manufacture of various articles, whether for use or ornament, aluminum is usually mixed with an alloy, as zinc, copper and antimony, for the purpose of making it hard and durable, but whether the aluminum be used in a pure state or be alloyed with another metal my improved method is applicable for plating upon the surface of such pure or alloyed aluminum.

In the practice of my invention certainsolutions and baths are used, the first being what 'I call a cleaning solution or pickle and is prepared as follows: To each gallon of water used add three and one-half ounces of oil of vitriol andeight pennyweights of boracic acid,

' these being well stirred together In this pickle the article to be plated is suspended and allowed to remain for about an hour. A rinsing solution of potash of a density of 12 by hydrometer is prepared and kept in a separate vessel, preferably a kettle having a 'coiled steam pipe in the bottom so that this solution may be kept at a temperature of at least 212 Fahrenheit. For washing the articles a tub or tank of runningwater, preferably prepared with a delivery tube discharging in the bottom of the tank and an overflow formed at the top is provided, the object of this being to have all of the waste material washed off from the article and carried away by the flow of the water. vided what I term a dark dip which should be kept at a temperature of about 100 .Fahrenheit, there being preferably used a kettle with a pipe leading into it to heat the solution and within the kettle a jar, the latter holding the dip. This dark dip is made by mixing with each gallon of sulphuric acid four pounds of nitrate of soda, two ounces of muriatic acid and three and one-half pennyweights of flaky carbon, as soot. The acid must stand at by hydrometer. The object of the carbon (soot) in this dark dip is topreserve the white color of the metal and to keep it from corroding, while the nitrate of soda dissolving freely in the sulphuric acid has about the same function as nitric acid when used as a dip for articles of German silver or copper.

After the article to be plated has been treated in the above solutions ahd dips in a manner which will be hereinafter describedit is subjected to treatment in what I call the whiteners, two of the latter being used and compounded and prepared as follows: The first whitener is prepared by mixing with one gallon of water one and one-half pounds of concentrated liquid ammonia and four pounds of cyanide of potassium, three and one-half pounds of' chloride of *zinc, five ounces of carbonate of potassium and eight pennyweights of white arsenic. This same There is also pro-L proportion of the several ingredients to the 1 gallon will be preserved in mixing up a larger quantity. If it shall be found on test that .the metal used as a plate does not deposit promptly and evenly the whitener should i have a slight proportion more of ammonia mixed with the solution, this precise quantity of ammonia required in the whitener for treating difierent alloys of aluminum beingto a slight degree only a matter of experiment and skill. This first whitener should be of a density of about 10 by hydrometer test and should be kept at a temperature of about Fahrenheit. A second whitener is prepared by mixing with each gallon of cold water onehalf gallon of concentrated ammonia, two poundsof cyanide of potassium, twelve ounces of carbonate of soda, four ounces of chloride of copper and five pennyweights of white arsenic; the above proportion of chloride of copper to be increased slightly to provide a more perfect deposit of copper. If the copper plate blisters intrease slightly the proportion of cyanide of potassium. This solution fills up the pores of the metal, protects the slight percentage of iron present in the aluminum and brings up a good, clear color on the work. This second whitener should stand at a density of about 10 by hydrometer and should be kept at a temperature of about 100 Fahrenheit.

Iron kettles are preferred for holding the whiteners, and the desired colors designed to be produced by the use of these whiteners can be brought out by increasing slightly the temperature of the solution.

H In the accompanying drawings the letterA denotes the solution termed a pickle; the letter B, the water bath; 0, the potash solution, and D the dip, and an article to be plated is treated in these several solutions in the order denoted by the letters. It is first placed in the pickle A and allowed to remain there for about an hour; second, it is then rinsed in B, then, third; quickly dipped into the potash solution and promptly removed; then, fourth,itis washed in the waterB; then, fifth, 5 plunged once or twice into the carbon dip D,

and, sixth, finally again washed in water B.

The letterE denotes abatter or like source of electric energy; F, a switch board; 9, the negative conductor; h, the positive wire; I, the zinc whitener, and K the copper whitener. The solutions in these whiteners are arranged in suitable vessels, the positive wire having suspended from it in the one bath the zinc anodest' z" and in the other the copper anodes 4 5 k 70. The negative rod L is connected to the negative wire g and arranged so that the articles to be whitened are suspended from this rod.

Having prepared an article in the dips and solutions before described it is suspended from the rod L until from the action of the solution it is seen that a sufficient layer has been deposited, this being a matter which calls for the skill of the plater in his knowledge of the art. Then remove the article from the zinc whitener and rinse it in cold water. Then suspend the article from the negative rod L in the copper whitener and deposit in that bath a layer of copper. The article, whether it be of pure aluminum or aluminum alloy, is now ready for the plating pf other metal, as gold, silver, nickel, or the ike.

Careful and thorough tests of the methods and means above described have shown that a layer of any of the other metals may be plated upon the aluminum and a perfect adhesion of the plating layer scoured that may be rolled, bent or otherwise subjected to severe compression or tensile or twisting strains without cracking, blistering or peeling off.

I claim as my invention 1. The method ofpickling aluminum to prepare it for plating which consists in subjecting the metal to treatment in a bath consisting of a solution in each gallon of water, of three and one half ounces of sulphuric acid, and eight penny-weights of boracic acid, all substantially as described.

2. As a step in the method of preparing aluminum for plating the immersion of the metal in a solution made up in the proportion of one gallon of sulphuric acid, four pounds of nitrate of soda, two ounces of mu riatic acid, and three and one half pennyweights of flaky carbon as soot, ot a density of substantially 50 by hydrometer, all substantially as described.

3. As a step in the method of preparing aluminum for plating, the immersion of the metal in a solution of sulphuric acid, nitrate of soda, muriatic acid and flaky carbon as soot, all substantially as and for the purpose described.

4:. As astep in the preparation of aluminum for plating, the treatment of the metal in an electro plating bath consisting of the following ingredients in the proportions stated, one gallon of water, one and one half pounds of concentrated liquid of ammonia, four pounds of cyanide of potassium, three and one-half pounds of chloride of zinc, five ounces of carbonate of potassium, and eight pennyweights of white arsenic,all substantially as described.

5. As astep in the preparation of aluminum for plating, the treatment of the metal in an electro plating hath made up in the proportions substantially of one gallon of water, one and one half gallons of concentrated ammonia, two pounds of cyanide of potassium, twelve ounces of carbonate of soda, four pounds of chloride of copper, and five pennyweights of white arsenic, all substantially as described.

6. The method of plating aluminum which consists first, in subjecting the metal to treatment in a pickling bath consisting of a solution of three and one half ounces of sulphuric acid, eight pennyweights of boracic acid to each gallon of water, then rinsing the article in water, then rinsing the article in a warm solution of potash, then washing the article in water, then treating it in a bath consisting in a solution substantially to each gallon of sulphuric acid of four pounds of nitrate of soda, two ounces of muriatic acid, and three and one half pennyweights of flaky carbon as soot, then plating it in a bath consisting substantially to each gallon of water of one and one half pounds of liquid ammonia four pounds of cyanide of potassium, three and one half pounds of chloride of zinc, five ounces of carbonate of potassium, and eight pennyweights of white arsenic, then furtherplatin g the article in a bath compounded substantially by mixing with each gallon of water, one and one half gallons of concentrated ammonia, ing it, then treating itin a solution in which two pounds of cyanide of potassium, twelve flaky "carbon, as soot, is an ingredient, then ounces of carbonate of soda, four ounces of plating the metal with alayer of zinc, then chloride of copper and five pennyweights of plating it with a layer of copper, then rinsing 15 5 white arsenic, and then finally coating with the metal, and finally plating in an ordinary the desired metal in a plating bath in the orbath with a metal desired, all substantially as dinary manner, all substantially as described. described.

7. The method of plating aluminum which WILLIAM H. LEGATE. consists in subjecting the metal to treatment Witnesses:

IO in a pickling bath, then rinsing the metal, CHAS. L. BURDETT,

then washing in a potash solution then wash--l ARTHUR B. JENKINS. v 

